A bag of icing sugar sparked a chemical scare that closed off a busy Wimbledon road during rush hour.

Police officers and four fire engines sealed off Lower Downs Road at 6pm last Monday after an unknown white substance was found in a woman's home.

The woman raised the alarm when she began to feel unwell, with symptoms including vomiting, diarrhoea, sweating and the shakes.

Concerned that her symptoms were linked to a bag of white powder that been hurled through her window and split on landing, the woman contacted police.

The 30-year-old, who asked not to be named, said: "If anyone found a big bag of white powder in their house they would do the same thing.

"I'm not a scientist. I don't know what it is." Fire engines, police and a decontamination specialist from the London Ambulance Service (LAS) descended on Lower Downs Road to investigate.

The road, which is a popular cut-through for drivers and pedestrians heading to Kingston Road or Wimbledon town centre, was cordoned off for an hour.

It was reopened when the substance was found to be icing sugar.

An LAS spokesman said: "We have to treat any potential chemical incident as if it's very serious, just in case. Nine times out of 10 it won't be a chemical."

Shane Heynie, 25, a South African resident from Lower Downs Road, said: "I wasn't worried. The British can exaggerate a lot. Silly things like this happen in South Africa all the time.

"They wouldn't shut off a road until they knew for sure what the problem was."